Polycarbonates are polymers obtained by combining aromatic or aliphatic dioxy compounds by means of a carbonate. Out of these, a polycarbonate obtained from 2,2-bis(4-hydroxyphenyl)propane (commonly called “bisphenol A”) (may be referred to as “PC-A” hereinafter) is used in many fields because it has excellent transparency, heat resistance and impact resistance.
Polycarbonates are generally manufactured from raw materials obtained from oil resources. The depletion of oil resources is now apprehended, and a polycarbonate manufactured from a raw material obtained from biogenic matter such as plants is desired. Therefore, a polycarbonate resin obtained from an ether diol which can be manufactured from a sugar is now under study.
For example, an ether diol represented by the following formula (5) is easily formed from biogenic matter such as a sugar or starch.
It is known that this ether diol has three stereoisomers. They are 1,4:3,6-dianhydro-D-sorbitol (to be referred to as “isosorbide” hereinafter) represented by the following formula (9), 1,4:3,6-dianhydro-D-mannitol (to be referred to as “isomannide” hereinafter) represented by the following formula (10), and 1,4:3,6-dianhydro-L-iditol (to be referred to as “isoidide” hereinafter) represented by the following formula (11).

Isosorbide, isomannide and isoidide are obtained from D-glucose, D-mannose and L-idose, respectively. For example, isosorbide can be obtained by hydrogenating D-glucose and then dehydrating it with an acid catalyst.
Out of the above ether diols represented by the formula (5), the introduction of isosorbide into a polycarbonate has been studied. JP-A 56-55425 (patent document 1) discloses a homopolycarbonate containing isosorbide. This homopolycarbonate has high specific viscosity and extremely high melt viscosity due to the rigid structure of its isosorbide skeleton, thereby making it difficult to mold it.
To overcome the above defect of the homopolycarbonate, copolymerization with various bishydroxy compounds is proposed. JP-A 56-110723 (patent document 2) proposes a copolycarbonate of isosorbide and an aromatic bisphenol. When the aromatic bisphenol is copolymerized, heat stability is improved but melt viscosity is not improved, whereby moldability becomes unsatisfactory. The aromatic bisphenol has a problem that it is derived from petroleum.
JP-A 2003-292603, WO2004/111106 and JP-A 2006-232897 (patent documents 3 to 5) propose a copolycarbonate of isosorbide and an aliphatic diol. When the aliphatic diol is copolymerized, melt viscosity lowers and moldability improves. However, most aliphatic diols are derived from petroleum, and diols which can be biogenic matter are limited to those having a relatively small number of carbon atoms, such as propanediol and butanediol. Since the boiling points of these aliphatic diols are lower than that of isosorbide, when they are polymerized by a melt ester interchange method, unreacted aliphatic diols are distilled off from a reaction system and the composition ratios of the obtained polymers become different from the charge ratios. When an aliphatic diol is copolymerized, heat stability tends to lower as well.
An isosorbide-containing polycarbonate contains a large number of oxygen atoms and has higher polarity than a polycarbonate obtained from a diol having no ether moiety, such as PC-A. Therefore, the isosorbide-containing polycarbonate has higher hygroscopic nature than PC-A, whereby it readily causes the deterioration of the dimensional stability of its molded product by moisture absorption and the deterioration of the heat resistance of the molded product at the time of wet heating. Further, as the isosorbide-containing polycarbonate has low surface energy, its molded product is easily stained and has low abrasion resistance. This surface energy can be evaluated by the contact angle with water.
The isosorbide-containing polycarbonate has still room for the improvement of heat stability and moldability as described above. The isosorbide-containing polycarbonate also has room for the improvement of some defects caused by low surface energy including low moisture absorption resistance.
(patent document 1) JP-A 56-55425
(patent document 2) JP-A 56-110723
(patent document 3) JP-A 2003-292603
(patent document 4) WO2004/111106
(patent document 5) JP-A 2006-232897